Truss structure



Feb. 1o, 1931.

L. C. MILBURN TRUSS' STRUCTURE Filed Jan. 27, 1928 Patented Feb. 10, 1931 `UNITED STATES PATENT vOFFICE LESSITER C. MILBUBN, F WICKLIFFE, OHIO, ASSIGNOR TO THE GLENN L. MARTIN COMPANY, OF CLEVELAND, OHIO, A GORPORATION 0F OE'IOv TRUSS STRUCTURE Application led January 27, 1928. Serial No. 249,820.

This invention relates to improvements in truss structures, particularly lightweight metal members for use in air craft where the strength-weight ratio must be high. A principal object of the invention is the s provision of members made up chiefly of thin metal parts so formed and proportioned as to give maximum strength for the weight of metal employed. l

Another object is the provision of a novel composite chordstructure having reinforcements both within and without the principaltransverse web portion, the reinforcements on the inner side of a chord element serving also as fins for attachment of the struts.

Another object is the provision of a built up structural member for use as a strut in the truss, but capable of use in other connections also.

Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawing, in which- Fig. 1 is a perspective view of a portion of afmetal truss structure embodying the invention; and

Fig. 2 is a detail sectional view on a larger scale illustrating particularly the construction of one of the composite structural members A which I employ as struts, the section being taken substantially on the line 2-2 of Fi l; and

ig. 3 is a detail sectional View on a larger scale illustrating particularly the construction of. a composite structural member B which I employ to meet localized stress conditions, the section being taken substantially on the line 3 3 of Fig. 1.

The beam illustrated in the drawing'is prefl erably formed throughout of aluminum alloy, when employed for air craft work. It has upper and lower chord members of identical form. These chord members each include an 10 'may be fabricated fromv an extruded or milled shape, and has short edge Bauges 12 ,and intermediate fins 13, all extending inwardly of the beam. The ns 13 are of sui'- inner part 10 and an outer part 11. The part cient width to constitute good anchorages for the struts of the beam, but in the-regions between such strutconnections these fins may be of reduced width, as shown at 14, in order to save weight. The outer part 11 of each chord consists of a transversely arched member, which may be formed by extrusion or braking and which is secured to the part 10 along the edges of the latter by 'any suitable means, as by rivets 15.

The strutsjof the beam are made up of thin sheet metal parts, preferably of the novel construction illustrated, in which there are two channel elements 16 with their web portions arranged back to back and secured to,- gether by rivets or the like. These channels have parallel flanges 17 that do not extend direct y from the webs but are attached thereto by intermediate forwardly and outwardly inclined portions 18. The edges of the anges 17 are curled or deiiected toward' the inside of the channel for the purpose of preventing crinkling or local bending of the thin metal under compression strains.

The intermediate portions 18 on each side of the member together constitute half of the wall of a tube-like section, the other half being constituted by a separate element having attaching flanges 19 in one plane and an l the same thickness as the fins 13. Consequently theV removal or omission of rivets and washers at the endsof thestruts enables l the tube-like sections of the struts to straddle the fins 13, after which the rivets are replaced extending through the fins instead of through the washers. In this manner the struts are mly and rigidly attached to the chord mem- As is well known theloads u on a beam differ considerably throughout tliJe length of the beam. In order to take care of this condition and at the same time economize we1ght as much as possible, I vary the proportions of The thickness of sheet metal employed in the manufacture of these struts may vary also, lif desired. On account of the smaller tube-like sections in strut B the web portions ofthe channels 16 of that strut are necessarily wider than the corresponding portions 16 of strut A. l have found it -to'be of advantage in this lighter construction to space the channels 16 apart somewhat by means of interposed spacing washer-s 23, through which ,the securing rivets 24 extend. I also preferably form flanged holes 25 in Ithe web portions of the channels of this strut for stifl'ening and lightening the same. Y

While in the accompanyin drawing and in the foregoing description have disclosed one form of my invention in considerable detail, this has been done for purposes of i1lus tration only and is not intended to constitute any limitation upon the invention;

Having thus described my invention, what I claim is:

l. A strut comprisin a pair of like channels arranged back to ack and secured together, the side flanges of the channels being attached to the webs thereof by intermediate laterally and outwardly extending portions, the aligned channel fianges on each side of the member joined in spaced relation to and by an element 1 having aligned attaching flanges and an intermediate laterally deflected portion, whereby a pair of spaced parallel tube-like sections are formed in the member.

2. A strut comprising a pair of like channels arranged backto back and secured together, the side flanges of the channels being attached to the webs thereof by intermediate laterally and outwardly extending portions,

an elemeuthaving attaching flanges in one plane and an intermediate portion comprising two parts each of which -is substantially complementary to the said intermediate portions of the channels, one of said last named elements being attached at its flanges to and in spaced relation with the aligned channel flanges on each side of the member, whereby a pair of spaced parallel tube-like sections are formed 1n the member. 3. A strut com rising a. pair of like channels arranged bac to, back, spaced a art and secured together, the side flanges of t e channelsbeing attached to lthe webs thereof b intermediate laterally and outwardly exten `of said web and ing portions, an element having attaching flanges in one plane and an intermediate out- Wardl deflected portion, one of said last name elements being attached by its flanges to the aligned channel flanges on each side of the structural member with spacers int'erposed between the flanges of said element and the flanges of said channels, whereby a pair of spaced parallel tube-like square sections are formed in the member.

4. A strut comprising'a pair of tube-like thin metal sec-tions joined together'by two webs spaced apart, said tube-like sections being each formed partially of continuations partially of separate upwardl arched elements having flanges joined to said'continuations with spacers interposed between the fianges of said elements and said continuations.

5. In a light metal truss structure, composite chord members each comprising inner and outer parts secured together along their edges, the outer part being arched transversely of the chord, the inner part having intermedia-te inwardly extending longitudinal fins, and tubular struts straddling said fins and joining said chord members, said struts being secured at their ends to said fins.

6. In a light metal truss structure, chord members each comprising inner and outer elements secured together along their edges, the outer element part being arched transversely of the inner element, the inner part having inwardly extending intermediate longitudinal fins, struts comprising twin tube-like sections split at their ends to straddle said fins, and fastenings extending through said fins and the straddling portions of said tube-like sections.

7. In a light metal truss structure, chord members comprising inner and outer parts secured together along their edges, the inner part-of each chord having a air of inwardly extending spaced longitu inall fins, and

struts joining said chord members, cach strut comprising a pair of spaced tube-like sections joined together by a web, the tube-like Asections being split to straddle said fins, and fastenin s extending through said fins and the stradling portions of said tube-like sections.

In testimony whereof, I hereunto afiix my signature.

LESSITER C. MILBURN. 

